1. Field of the Invention
This invention relates to a pneumatic tire and more particularly to a relatively high speed and heavy duty bias tire for use in trucks, buses, construction vehicles and the like, wherein the form of grooves forming the tread pattern is improved and thereby the probability of cracks in the bottoms of the grooves is reduced to a minimum and an extended durability and a higher degree of safety are assured.
2. Prior Art
Tread patterns such as rib type, lug type, etc. have important effects on tire performances such as rolling resistance, steering property, stability, tractive ability, braking power and so forth. Accordingly, various studies have been directed to the tread pattern itself so as to improve those performances successfully.
On the other hand, it is often seen that cracks occur in the bottoms of the grooves in the tread pattern of relatively high speed and heavy duty tires for use in trucks, buses, and construction vehicles and more particularly sand conveying tires, which results in the inability to travel. Heretofore, the problems were coped with by merely changing the composition of the rubber without tracing the reasons for the cracks, and it cannot be said that a truly satisfactory countermeasure has been offered.